Some effects of basic multicellular unit-based remodelling on photon absorptiometry of trabecular bone.

This article offers algorithms and an algebra for estimating effects of bone turnover, remodelling space, undermineralized bone and trabecular surface-to-volume ratio effects on trabecular bone mass estimation by photon absorptiometry. From published histomorphometric data and other evidence the algorithms suggest the amount of mineral in a given bone sample can suggest to absorptiometry an amount of bone that differs from the truth by over 40% in the extreme, and more commonly by 5-15%. They suggest that by reducing a bone's global mineral content high bone turnover causes underestimation of true bone mass. They suggest that by letting mineral return to the remodelling space and undermineralized bone, reduced bone turnover causes apparent gains in bone mass. The commonly suggested 5-15% magnitude of such errors exceeds those assumed in the past. The algorithms suggest that after a challenge to remodelling those bone mineral changes can take from 6 months to over 3 years to reach steady states. Those features could explain why many osteoporosis treatments judged effective from initial absorptiometric evidence failed when used for long periods in patients. Finally the algorithms suggest that a real increase in ideal bone volume can even appear to absorptiometry as no gain or an initial loss, which has already happened in two human experiments.